Wind power converter device and converter device

ABSTRACT

A wind power converter device is provided. The wind power converter device includes grid side converters, generator side converters and a DC bus module. Each of the grid side converters includes grid side outputs electrically coupled to a grid and a first and a second DC inputs. Each two of the neighboring grid side converters are connected in series at the second and the first DC inputs. Each of the generator side converters includes generator side inputs electrically coupled to a generator device and a first and a second DC outputs. Each two of the neighboring generator side converters are coupled in series at the second and the first DC outputs. The DC bus module is electrically coupled between the grid side converters and the generator side converters.

RELATED APPLICATIONS

This Application is a Divisional of U.S. application Ser. No.14/794,844, filed on Jul. 9, 2015, and claims priority to ChineseApplication Serial Number 201410452474.X, filed Sep. 5, 2014 and ChineseApplication Serial Number 201510094313.2, filed Mar. 3, 2015, which areherein incorporated by reference.

BACKGROUND Field of Invention

The present invention relates to a converter technology. Moreparticularly, the present invention relates to a wind power converterdevice and a converter device.

Description of Related Art

Along with the development of the renewable power, technicians focus onthe improvement of the wind power converter, which is the core of thewind power generation system. In the field of the electricity-drivenfrequency converter and the converter for generating power, a multipleof converters are used based on the increasing system capacity. However,a multiple of direct current (DC) buses that extend for a long distanceare used to transmit the voltage when a multiple of converters are used.If the cost of the transmission of the energy in the DC component cannot be lowered, the efficiency of the whole converter can not beimproved. In addition, when the distance between the motor and thegenerator is longer, i.e. the distance between the converters in thegenerator side and the converters in the motor side is longer, amultiple of direct current (DC) buses that extend for a long distanceare used to transmit the voltage when a multiple of converters are used.If the cost of the transmission of the energy in the DC component cannot be lowered, the efficiency of the whole converter can not beimproved.

Accordingly, what is needed is a wind power converter device and aconverter device to address the issues mentioned above.

SUMMARY

The disclosure provides a wind power converter device. The wind powerconverter device includes a plurality of grid side converters, aplurality of generator side converters and a DC bus module. The gridside converters each includes a plurality of grid side outputselectrically coupled to a grid, a first direct current (DC) input and asecond DC input, wherein the second DC input of one of any two of theneighboring grid side converters is coupled in series to the first DCinput of another one of the two neighboring grid side converters. Thegenerator side converters each includes a plurality of generator sideinputs electrically coupled to a generator device, a first DC output anda second DC output, wherein the second DC output of one of any two ofthe neighboring generator side converters is coupled in series to thefirst DC output of another one of the two neighboring generator sideconverters. The DC bus module is electrically coupled between the gridside converters and the generator side converters.

Another aspect of the present disclosure is to provide a wind powerconverter device. The wind power converter device includes n grid sideconverters, 2n generator side converters and a DC bus module. The n gridside converters each includes a plurality of grid side outputselectrically coupled to a grid, a first DC input, a middle point inputand a second DC input. The 2n generator side converters each includes aplurality of generator side inputs electrically coupled to a generatordevice, a first DC output and a second DC output, wherein the second DCoutput of the 2n−1-th generator side converters is coupled in series tothe first DC output of the 2n-th generator side converters. The DC busmodule is electrically coupled between the grid side converters and thegenerator side converters, wherein n>=1.

Another aspect of the present disclosure is to provide a wind powerconverter device. The wind power converter device includes 2n grid sideconverters, n generator side converters and a DC bus module. The 2n gridside converters each includes a plurality of grid side outputselectrically coupled to a grid, a first DC input and a second DC input,wherein the second DC input of the 2n−1-th grid side converters iscoupled in series to the first DC input of the 2n-th grid sideconverters. Each of the n generator side converters includes a pluralityof generator side inputs electrically coupled to a generator device, afirst DC output, a middle point output and a second DC output. The DCbus module electrically coupled between the grid side converters and thegenerator side converters, wherein n>=1.

Another aspect of the present disclosure is to provide a converterdevice. The converter device includes a plurality of first generatorside converters, a plurality of second generator side converters and aDC bus module. The first generator side converters each includes aplurality of motor side outputs electrically coupled to a motor device,a first DC input and a second DC input, wherein the second DC input ofone of any two of the neighboring first generator side converters iscoupled in series to the first DC input of another one of the twoneighboring first generator side converters. The second generator sideconverters each includes a plurality of generator side inputselectrically coupled to a generator device, a first DC output and asecond DC output, wherein the second DC output of one of any two of theneighboring second generator side converters is coupled in series to thefirst DC output of another one of the two neighboring second generatorside converters. The DC bus module is electrically coupled between thefirst generator side converters and the second generator sideconverters.

These and other features, aspects, and advantages of the presentdisclosure will become better understood with reference to the followingdescription and appended claims.

It is to be understood that both the foregoing general description andthe following detailed description are by examples, and are intended toprovide further explanation of the disclosure as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure can be more fully understood by reading the followingdetailed description of the embodiment, with reference made to theaccompanying drawings as follows:

FIG. 1 is a circuit diagram of a wind power converter device in anembodiment of the present disclosure;

FIG. 2 is a block diagram of the secondary generator side control modulein an embodiment of the present disclosure;

FIG. 3 is a block diagram of the primary generator side control modulein an embodiment of the present disclosure;

FIG. 4 is a circuit diagram of a wind power converter device in anembodiment of the present disclosure;

FIG. 5 is a block diagram of the generator side control module in anembodiment of the present disclosure;

FIG. 6 is a circuit diagram of a wind power converter device in anembodiment of the present disclosure;

FIG. 7 is a circuit diagram of a wind power converter device in anembodiment of the present disclosure;

FIG. 8 is a circuit diagram of a wind power converter device in anembodiment of the present disclosure;

FIG. 9 is a circuit diagram of a wind power converter device in anembodiment of the present disclosure;

FIG. 10 is a circuit diagram of a wind power converter device in anembodiment of the present disclosure;

FIG. 11 is a circuit diagram of a wind power converter device in anembodiment of the present disclosure; and

FIG. 12 is a circuit diagram of a converter device in an embodiment ofthe present disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to the present embodiments of thedisclosure, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers are used in thedrawings and the description to refer to the same or like parts.

Reference is now made to FIG. 1. FIG. 1 is a circuit diagram of a windpower converter device 1 in an embodiment of the present disclosure. Thewind power converter device 1 includes grid side converters 10A-10C,generator side converters 12A-12C and a DC bus module. The grid sideconverters 10A-10C and the generator side converters 12A-12C arerespectively disposed in the up part of the tower and the under part ofthe tower (Under Wind). The generator side converters 12A-12C aredisposed in a room of the top of the tower of the wind power converterdevice 1 (Upwind). The grid side converters 10A-10C are disposed in thebottom or outside of the tower of the wind power converter device 1. Thecost of the cables for transmitting power between the grid sideconverters 10A-10C and the generator side converters 12A-12C can bereduced. The loading of the weight of the up part of the tower can bedistributed equally as well.

In an embodiment, all the grid side converters 10A-10C include identicalcomponents. Take the grid side converter 10A as an example, the gridside converter 10A in the present embodiment is a two-level converterand includes grid side outputs (e.g. three grid side outputs) N1-N3electrically coupled to the grid 16, a first DC input IN1 and a secondDC input IN2. In an embodiment, the grid side outputs N1-N3 areelectrically coupled to the grid 16 through a voltage transformer 160.

The second DC input IN2 of one of any two of the neighboring grid sideconverters 10A-10C is coupled in series to the first DC input IN1 ofanother one of the two neighboring grid side converters 10A-10C. Takethe grid side converters 10A and 10B as an example, the second DC inputIN2 of the grid side converter 10A is coupled in series to the first DCinput IN1 of the grid side converter 10B. Similarly, the second DC inputIN2 of the grid side converter 10B is coupled in series to the first DCinput IN1 of the grid side converter 10C.

In an embodiment, the number of the generator side converters 12A-12C isthe same as the number of the grid side converters 10A-10C. Further, allthe generator side converters 12A-12C may include the identicalcomponents. Take the generator side converter 12A as an example, thegenerator side converter 12A in the present embodiment is a two-levelconverter and includes generator side inputs (e.g. three generator sideinputs) O1-O3 electrically coupled to the generator device 18, a firstDC output OUT1 and a second DC output OUT2. In an embodiment, thegenerator device 18 is a permanent magnet synchronous generator device,an excitation synchronous generator device or an induction generatorhaving a multiple groups of windings. Each group of the windingsincludes three windings (not illustrated). Take the generator sideconverter 12A as an example, the three windings of each group ofwindings in the generator device 18 in the present embodiment arerespectively coupled to the generator side inputs O1-O3. In anembodiment, the generator side converters 12A-12C are electricallycoupled to the generator device 18 through a filtering circuit (notillustrated) that includes such as an inductor or a capacitor.

The second DC output OUT2 of one of any two of the neighboring generatorside converters 12A-12C is coupled in series to the first DC output OUT1of another one of the two neighboring generator side converters 12A-12C.Take the generator side converters 12A and 12B as an example, the secondDC output OUT2 of the generator side converter 12A is coupled in seriesto the first DC output OUT1 of the generator side converter 12B.Similarly, the second DC output OUT2 of the generator side converter 12Bis coupled in series to the first DC output OUT1 of the generator sideconverter 12C.

The DC bus module in the present embodiment includes only two buses 140and 142 corresponding to the two grid side converters 10A and 10C andthe two generator side converters 12A and 12C. The bus 140 iselectrically coupled to the first DC input IN1 of the grid sideconverter 10A and the first DC output OUT1 of the generator sideconverters 12A. The bus 142 is electrically coupled to the second DCinput IN2 of the grid side converter 10C and the second DC output OUT2of the generator side converters 12C. The DC bus is not disposed betweeneach pair of the first DC input IN1, the first DC output OUT1, thesecond DC input IN2 and the second DC output OUT2 that corresponds tothe intermediate grid side converter and generator side converter.

In an embodiment, the DC bus module further include bus capacitors C1-C6each electrically coupled between the first DC inputs IN1 and the secondDC inputs IN2 of the grid side converters 10A-10C and between the firstDC outputs OUT1 and the second DC outputs OUT2 of the generator sideconverters 12A-12C to support the voltages of these terminals.

In an embodiment, the wind power converter device 1 further includeschopper circuits 13A, 13B and 13C each disposed at the two ends of thebus capacitors C4, C5 and C6 to perform a voltage balancing protectionto the generator side converters 12A-12C. Take the chopper circuit 13Aas an example, the chopper circuit 13A includes a controllable powersemiconductor switch, a resistor and two diodes. The collector of thecontrollable power semiconductor switch electrically connects thecathode of one diode and one terminal of the bus capacitor C4, and theemitter of the controllable power semiconductor switch electricallyconnects the anode of the diode. One terminal of the resistor connectsthe emitter of the controllable power semiconductor switch and the otherterminal of the resistor connects the other terminal of the buscapacitor C4. The other diode connects the resistor in parallel. In someembodiments, the wind power converter device 1 further includes choppercircuits each electrically coupled to the two ends of each of the buscapacitors between the first and the second DC inputs of each of thegrid side converters or between the two ends of each of the buscapacitors of the bus capacitors between the first and the second DCoutputs of the generator side converters to perform a voltage balancingprotection to the grid side converters and the generator sideconverters.

Therefore, the wind power converter device 1 of the present disclosurecan connect the grid side converters 10A-10C in series by electricallycoupling the first DC input IN1 and the second DC input IN2 of any twoneighboring grid side converters 10A-10C, and can connect the generatorside converters 12A-12C in series by electrically coupling the first DCoutput OUT1 and the second DC output OUT2 of any two neighboringgenerator side converters 12A-12C.

Further, since the buses 140 and 142 are only disposed between the firstDC input IN1 of the grid side converter 10A and the first DC output OUT1of the generator side converter 12A and between the second DC input IN2of the grid side converter 10C and the second DC output OUT2 of thegenerator side converter 12C, the DC voltages of the grid sideconverters and the generator side converters can be adjusted accordingto the number of the grid side converters and the generator sideconverters coupled in series. The design of the wind power converterdevice 1 can be more flexible. The number of the DC buses between thegrid side converters 10A-10C and the generator side converters 12A-12Cand the cost can be reduced.

In an embodiment, the generator side converters 12A-12C illustrated inFIG. 1 include a primary generator side converter and a plurality ofsecondary generator side converters. In an embodiment, the generatorside converter 12C can be assigned to be the primary generator sideconverter, such that the generator side converters 12A and 12B becomethe secondary generator side converters.

The detail description of the control mechanism of the primary generatorside converter and the secondary generator side converters isillustrated in the following paragraphs.

The wind power converter device 1 further includes secondary generatorside control modules 11A and 11B and the primary generator side controlmodule 11C corresponding to the secondary generator side converters 12Aand 12B and the primary generator side converter 12C respectively.

The secondary generator side control modules 11A and 11B respectivelyreceive three phase secondary input current amounts I1-I2 correspondingto the generator side inputs O1-O3 of the corresponding secondarygenerator side converters 12A and 12B, a secondary DC voltage amountV_(dc) _(_) _(i) (i.e. the DC bus voltage) corresponding to the firstand the second DC outputs OUT1 and OUT2 of the corresponding secondarygenerator side converters 12A and 12B and a second axis general givencurrent component i_(q) _(_) _(norm*) outputted from the primarygenerator side converter 12C to generate three phase secondary voltagecontrol signals V1-V2 accordingly to control the corresponding secondarygenerator side converters 12A and 12B. Each of the secondary generatorside control modules 11A and 11B generates a second axis secondaryindependent given current component i_(q) _(_) _(i*) according to thecorresponding secondary DC voltage amount V_(dc) _(_) _(i).

In an embodiment, both of the secondary generator side control modules11A and 11B include identical architecture. The detail description ismade by using the secondary generator side control module 11A as theexample.

Reference is now made to FIG. 2. FIG. 2 is a block diagram of thesecondary generator side control module 11A in an embodiment of thepresent disclosure. The secondary generator side control module 11Aincludes a current retrieving unit 200, a first converting unit 202, afirst computing unit 204, a voltage retrieving unit 206, a voltagedifference computing unit 208, a voltage control unit 210, a secondcomputing unit 212, a first current control unit 214, a second currentcontrol unit 216 and a second converting unit 218.

The current retrieving unit 200 is electrically coupled to the generatorside inputs O1-O3 of the secondary generator side converter 12A toretrieve the three phase secondary input current amount I1. In anembodiment, the three phase secondary input current amount I1 includesthree components i_(a) _(_) _(i), i_(b) _(_) _(i) and i_(c) _(_) _(i).

The first converting unit 202 is configured to convert the threecomponents i_(a) _(_) _(i), i_(b) _(_) _(i) and i_(c) _(_) _(i) of thethree phase secondary input current amount I1 to a first axis secondarycurrent component i_(i) _(_) _(i) and a second axis secondary currentcomponent i_(q) _(_) _(i). In an embodiment, the first converting unit202 includes a dq rotation coordinate that comprises a d axis and a qaxis. The first axis secondary current component corresponds to the daxis of the dq rotation coordinate and the second axis secondary currentcomponent i_(q) _(_) _(i) corresponds to the q axis of the dq rotationcoordinate. In an embodiment, the first axis secondary current componenti_(d) _(_) _(i) is a reactive current component and the second axissecondary current component i_(q) _(_) _(i) is an active currentcomponent.

The first computing unit 204 is configured to perform computation togenerate a first axis difference i_(d) _(_) _(id) according to the firstaxis secondary current component i_(i) _(_) _(i) and a first axissecondary independent given current component i_(d) _(_) _(i). The firstaxis secondary independent given current component i_(d) _(_) _(i*) canbe a predetermined value stored in the secondary generator side controlmodule 11A.

The voltage retrieving unit 206 is configured to retrieve the secondaryDC voltage amount V_(dc) _(_) _(i) from the first and the second DCoutputs OUT1 and OUT2 of the secondary generator side converter 12A. Thevoltage difference computing unit 208 is configured to performcomputation to generate a voltage difference V_(dc) _(_) _(d) accordingto the secondary DC voltage amount V_(dc) _(_) _(i) and a referentvoltage amount V_(dc) _(_) _(ref). The referent voltage amount V_(dc)_(_) _(ref) can be a predetermined value stored in the secondarygenerator side control module 11A. Further, the voltage control unit 210is configured to generate the second axis secondary independent givencurrent component i_(q) _(_) _(i*) according to the voltage differenceV_(dc) _(_) _(d).

The second computing unit 212 is configured to perform computation togenerate a second axis difference i_(q) _(_) _(id) according to thesecond axis secondary current component i_(q) _(_) _(i), the second axisgeneral given current component i_(q) _(_) _(norm*) and the second axissecondary independent given current component i_(q) _(_) _(i*).

The first current control unit 214 is configured to generate a firstaxis secondary voltage control signal V_(d) _(_) _(i) according to thefirst axis difference i_(d) _(_) _(id). The second current control unit216 is configured to generate a second axis secondary voltage controlsignal V_(q) _(_) _(i) according to the second axis difference i_(q)_(_) _(id). The second converting unit 218 is configured to convert thefirst axis secondary voltage control signal V_(d) _(_) _(i) and thesecond axis secondary voltage control signal V_(q) _(_) _(i) to thethree phase secondary voltage control signal V1. In an embodiment, thethree phase secondary voltage control signal V1 includes threecomponents V_(a) _(_) _(i), V_(b) _(_) _(i) and V_(c) _(_) _(i). In anembodiment, each of the three components V_(a) _(_) _(i), V_(b) _(_)_(i) and V_(c) _(_) _(i) can be a pulse width modulation (PWM) signal.

Therefore, by using the three phase secondary voltage control signal V1to control the semiconductor switches in the secondary generator sideconverter 12A to be turned on or turned off, the secondary generatorside converter 12A operates in either a rectifying state, an invertingstate or a non-operation state.

It is noted that the secondary generator side control module 11B canalso generates the three phase secondary voltage control signal V2according to the three phase secondary input current amount I2, thesecond axis general given current component i_(q) _(_) _(norm*) and thesecondary DC voltage amount V_(dc) _(_) _(i). However, the first axissecondary independent given current component i_(d) _(_) _(i*) and thesecond axis secondary independent given current component i_(q) _(_)_(i*) that correspond to the secondary generator side control module 11Bcan be independent from those that correspond to the secondary generatorside control module 11A. And the second axis general given currentcomponent i_(q) _(_) _(norm*) can be used in both of the secondarygenerator side control modules 11A and 11B.

Reference is now made to FIG. 3. FIG. 3 is a block diagram of theprimary generator side control module 11C in an embodiment of thepresent disclosure. The primary generator side control module 11Cincludes a current retrieving unit 300, a first converting unit 302, afirst computing unit 304, a second computing unit 306, a first currentcontrol unit 308, a second current control unit 310, a second convertingunit 312.

The current retrieving unit 300 is electrically coupled to the generatorside inputs O1-O3 of the primary generator side converter 12C toretrieve the three phase primary input current amount I3. In anembodiment, the three phase primary input current amount I3 includesthree components i_(a) _(_) _(N), i_(b) _(_) _(N) and i_(c) _(_) _(N).

The first converting unit 302 is configured to convert the threecomponents i_(a) _(_) _(N), i_(b) _(_) _(N) and i_(c) _(_) _(N) of thethree phase primary input current amount I3 to a first axis secondarycurrent component i_(d) _(_) _(N) and a second axis secondary currentcomponent i_(q) _(_) _(N). In an embodiment, the first converting unit302 includes a dq rotation coordinate that comprises a d axis and a qaxis. The first axis primary current component I_(d) _(_) _(N)corresponds to the d axis of the dq rotation coordinate and the secondaxis primary current component i_(q) _(_) _(N) corresponds to the q axisof the dq rotation coordinate. In an embodiment, the first axis primarycurrent component i_(d) _(_) _(N) is a reactive current component andthe second axis primary current component i_(q) _(_) _(N) is an activecurrent component.

The first computing unit 304 is configured to perform computation togenerate a first axis difference i_(d) _(_) _(Nd) according to the firstaxis primary current component i_(d) _(_) _(N) and a first axis primaryindependent given current component i_(d) _(_) _(N*.)

The second computing unit 306 is configured to perform computation togenerate a second axis difference i_(q) _(_) _(Nd) according to thesecond axis primary current component i_(q) _(_) _(N), a total secondaxis secondary independent given current Σi_(q) _(_) _(i*) and a secondaxis general given current component i_(q) _(_) _(norm*). In anembodiment, the total second axis secondary independent given currentΣi_(q) _(_) _(i*) is the sum of the second axis secondary independentgiven currents i_(q) _(_) _(i*) of all the secondary generator sidecontrol modules 11A and 11B.

The first current control unit 308 is configured to generate a firstaxis primary voltage control signal V_(d) _(_) _(N) according to thefirst axis difference i_(d) _(_) _(Nd). The second current control unit310 is configured to generate the second axis primary voltage controlsignal V_(q) _(_) _(N) according to the second axis difference i_(q)_(_) _(Nd). The second converting unit 312 is configured to convert thefirst axis primary voltage control signal V_(d) _(_) _(N) and the secondaxis primary voltage control signal V_(q) _(_) _(N) to the three phaseprimary voltage control signal V3. In an embodiment, the three phaseprimary voltage control signal V3 includes three components V_(a) _(_)_(N), V_(b) _(_) _(N) and V_(c) _(_) _(N). In an embodiment, each of thethree components V_(a) _(_) _(N), V_(b) _(_) _(N) and V_(c) _(_) _(N)can be a pulse width modulation (PWM) signal.

Therefore, by using the three phase secondary voltage control signal V3to control the semiconductor switches in the primary generator sideconverter 12C to be turned on or turned off, the primary generator sideconverter 12C operates in either a rectifying state, an inverting stateor a non-operation state.

It is noted that the primary generator side control module 11C and thesecondary generator side control modules 11A and 11B can performcommunication by using various possible forms signal transmissionformats. The primary generator side control module 11C delivers thesecond axis general given current component i_(q) _(_) _(norm*) to thesecondary generator side control modules 11A and 11B. The secondarygenerator side control modules 11A and 11B deliver the second axissecondary independent given currents i_(q) _(_) _(i*) to the primarygenerator side control module 11C. In an embodiment, the primarygenerator side control module 11C performs addition operation on thesecond axis secondary independent given currents i_(q) _(_) _(i*)delivered by the secondary generator side control modules 11A and 11B togenerate the total second axis secondary independent given currentΣi_(q) _(_) _(i*).

Therefore, by using the method described above, the wind power converterdevice 1 perform efficient control on the primary generator sideconverter 12C and the secondary generator side converters 12A and 12Baccording to the operation of the primary generator side control module11C and the secondary generator side control modules 11A and 11B.

Reference is now made to FIG. 4. FIG. 4 is a circuit diagram of a windpower converter device 4 in an embodiment of the present disclosure. Thewind power converter device 4 includes grid side converters 10A-10C,generator side converters 12A-12C and a DC bus module. Similar to thewind power converter device 1 illustrated in FIG. 1, the grid sideconverters 10A-10C of the wind power converter device 4 are connected inseries and the generator side converters 12A-12C are connected inseries. Most of the components included in the wind power converterdevice 4 are identical to those included in the wind power converterdevice 1. As a result, only the description of components in the windpower converter device 4 that are different from those in the wind powerconverter device 1 is made.

In the present embodiment, the DC bus module includes DC buses 400, 402,404 and 406. The DC bus 400 is electrically coupled to the first DCinput IN1 of the grid side converter 10A and the first DC output OUT1 ofthe generator side converter 12A. The DC bus 402 is electrically coupledto the second DC input IN2 of the grid side converter 10A and the secondDC output OUT2 of the generator side converter 12A (which is equivalentto the first DC input IN1 of the grid side converter 10B and the firstDC output OUT1 of the generator side converter 12B).

The DC bus 404 is electrically coupled to the second DC input IN2 of thegrid side converter 10B and the second DC output OUT2 of the generatorside converter 12B (which is equivalent to the first DC input IN1 of thegrid side converter 10C and the first DC output OUT1 of the generatorside converter 12C).

The DC bus 406 is electrically coupled to the second DC input IN2 of thegrid side converter 10C and the second DC output OUT2 of the generatorside converter 12C.

The detail description of the control mechanism of the generator sideconverters 12A-12C is illustrated in the following paragraphs.

The wind power converter device 4 further includes generator sidecontrol modules 41A-41C each corresponding to one of the generator sideconverters 12A-12C. The generator side control modules 41A-41C generatethree phase voltage control signals V1-V3 according to three phase inputcurrent amounts I1-I3 corresponding to the generator side inputs O1-O3of the corresponding generator side converters 12A and 12C and thesecond axis general given current component i_(q) _(_) _(norm*). In anembodiment, the generator side control modules 41A-41C include identicalarchitecture. The detail description is made by using the generator sidecontrol module 41A as the example.

Reference is now made to FIG. 5. FIG. 5 is a block diagram of thegenerator side control module 41A in an embodiment of the presentdisclosure. The generator side control module 41A includes a currentretrieving unit 500, a first converting unit 502, a first computing unit504, a second computing unit 506, a first current control unit 508, asecond current control unit 510 and a second converting unit 512.

The current retrieving unit 500 is electrically coupled to the generatorside inputs O1-O3 of the generator side converter 12A to retrieve thethree phase input current amount I1. In an embodiment, the three phaseinput current amount I1 includes three components i_(a) _(_) _(i), i_(b)_(_) _(i) and i_(c) _(_) _(i).

The first converting unit 502 is configured to convert the threecomponents i_(a) _(_) _(i), i_(b) _(_) _(i) and i_(c) _(_) _(i) of thethree phase input current amount I1 to a first axis current componenti_(d) _(_) _(i) and a second axis current component i_(g) _(_) _(i). Inan embodiment, the first converting unit 502 includes a dq rotationcoordinate that comprises a d axis and a q axis. The first axis currentcomponent corresponds to the d axis of the dq rotation coordinate andthe second axis current component i_(q) _(_) _(i) corresponds to the qaxis of the dq rotation coordinate. In an embodiment, the first axiscurrent component is a reactive current component and the second axiscurrent component i_(q) _(_) _(i) is an active current component.

The first computing unit 504 is configured to perform computation togenerate a first axis difference i_(d) _(_) _(id) according to the firstaxis current component and a first axis independent given currentcomponent i_(d) _(_) _(i*).

The second computing unit 506 is configured to perform computation togenerate a second axis difference i_(q) _(_) _(id) according to thesecond axis current component i_(q) _(_) _(i) and the second axisgeneral given current component i_(q) _(_) _(norm*). In the presentembodiment, the second axis general given current component i_(q) _(_)_(norm*) is provided by an external control module (not illustrated).The generator side control module 41A can deliver the second axisgeneral given current component i_(q) _(_) _(norm*) received from theexternal control module to the generator side control modules 41B and41C. In the present embodiment, the generator side control module 41Aperforms communication with the generator side control modules 41B and41C. In other embodiments, the second axis general given currentcomponent i_(q) _(_) _(norm*) can be received by the generator sidecontrol module 41B or 41C from the external control module and can bedelivered to other generator side control modules.

The first current control unit 508 is configured to generate a firstaxis voltage control signal V_(d) _(_) _(i) according to the first axisdifference i_(d) _(_) _(d). The second current control unit 510 isconfigured to generate a second axis voltage control signal V_(q) _(_)_(i) according to the second axis difference i_(d) _(_) _(id). Thesecond converting unit 512 is configured to convert the first axisvoltage control signal V_(d) _(_) _(i) and the second axis voltagecontrol signal V_(q) _(_) _(i) to the three phase voltage control signalV1. In an embodiment, the three phase voltage control signal V1 includesthree components V_(a) _(_) _(i), V_(b) _(_) _(i) and V_(c) _(_) _(i).In an embodiment, each of the three components V_(a) _(_) _(i), Vb_ _(i)and V_(c) _(_) _(i) can be a pulse width modulation (PWM) signal.

Therefore, by using the three phase voltage control signal V1 to controlthe semiconductor switches in the generator side converter 12A to beturned on or turned off, the secondary generator side converter 12Aoperates in either a rectifying state, an inverting state or anon-operation state. The wind power converter device 4 can performefficient control on the generator side converters 12A-12C through thegenerator side control modules 41A-41C by using the method describedabove.

Reference is now made to FIG. 6. FIG. 6 is a circuit diagram of a windpower converter device 6 in an embodiment of the present disclosure. Thewind power converter device 6 includes grid side converters 10A-10B,generator side converters 12A-12B and a DC bus module. Similar to thewind power converter device 1 illustrated in FIG. 1, the grid sideconverters 10A-10B of the wind power converter device 6 are connected inseries and the generator side converters 12A-12B are connected inseries. Most of the components included in the wind power converterdevice 6 are identical to those included in the wind power converterdevice 1. The only difference is that both the number of the grid sideconverters 10A-10B and the generator side converters 12A-12B is two.

Most of the components included in the wind power converter device 6 areidentical to those included in the wind power converter device 1. Thedifference is that the DC bus module further includes an intermediate DCbus electrically coupled between the second DC input IN2 of the gridside converter 10A and the second DC output OUT2 of the generator sideconverter 12A.

It is noted that in addition to the examples that include the grid sideconverters and the generator side converters having the number of threeor two, the wind power converter device may include more number of gridside converters and the generator side converters in other embodimentsand can accomplish an efficient control mechanism by using the methoddescribed above.

Reference is now made to FIG. 7. FIG. 7 is a circuit diagram of a windpower converter device 7 in an embodiment of the present disclosure.

The architecture of the wind power converter device 7 is identical tothat of the wind power converter device 6 illustrated in FIG. 6. Thegrid side converters 70A-70B included in the wind power converter device7 are connected in series and the generator side converters 72A-72Bincluded in the wind power converter device 7 are connected in series.The difference between the wind power converter device 7 and the windpower converter device 6 is that the grid side converters 70A-70B andthe generator side converters 72A-72B included in the wind powerconverter device 7 are three-level converters. The generator sidecontrol modules 71A and 71B included in the wind power converter device7 can use the method described above to control the generator sideconverters 72A-72B.

Similarly, the architecture of the three-level converters can be used inthe wind power converter device 1 illustrated in FIG. 1 as well.

Reference is now made to FIG. 8. FIG. 8 is a circuit diagram of a windpower converter device 8 in an embodiment of the present disclosure.

The wind power converter device 8 includes a grid side converter 80A,generator side converters 82A-82B and a DC bus module. The generatorside converters 82A-82B are connected in series. However, the grid sideconverter 80A in the wind power converter device 8 is a three-levelconverter. The generator side converters 82A-82B are two-levelconverters. The second DC output OUT2 of the generator side converter82A and the first DC output OUT1 of the generator side converter 82B arecoupled in series. In the present embodiment, the DC bus module includestwo DC buses 800 and 802 corresponding to the generator side converters82A and 82B and the grid side converter 80A. The DC bus 800 iselectrically coupled to the first DC output OUT1 of the generator sideconverter 82A and the first DC input IN1 of the grid side converter 80A.The DC bus 802 is electrically coupled to the second DC output OUT2 ofthe generator side converter 82B and the second DC input IN2 of the gridside converter 80A. No DC bus is disposed between the second DC outputOUT2 of the generator side converter 82A and the first DC output OUT1 ofthe generator side converter 82B and the intermediate input IN0 of thegrid side converter 80A. In the present embodiment, the generator sidecontrol modules 81A and 81B included in the wind power converter device8 can use the methods described in FIG. 2 and FIG. 3 to control thegenerator side converters 82A-82B.

In an embodiment, the DC bus module further include bus capacitors C1-C4each electrically coupled between the first DC input IN1 and theintermediate input IN0 of the grid side converter 80A, between theintermediate input IN0 and the second DC inputs IN2 of the generatorside converters 80A, and between the first DC output OUT1 and the secondDC output OUT2 of the generator side converters 82A-82B to support thevoltages of these terminals.

In an embodiment, the wind power converter device 8 further includeschopper circuits 83A and 83B. The chopper circuits 83A and 83B arerespectively disposed between the two ends of the bus capacitor C3 andthe two ends of the bus capacitor C4 to perform a voltage balancingprotection to the generator side converters 82A-82B.

In an embodiment, the wind power converter device is similar to the windpower converter device 8 illustrated in FIG. 8 but includes the DC busmodule that has the DC buses 800, 801 and 802. The DC bus 800 iselectrically coupled to the first DC input IN1 of the grid sideconverter 80A and the first DC output OUT1 of the generator sideconverter 82A. The DC bus 801 is electrically coupled to theintermediate input IN0 of the grid side converter 80A and the second DCoutput OUT2 of the generator side converter 82A. The DC bus 802 iselectrically coupled to the second DC input IN2 of the grid sideconverter 80A and the second DC output OUT2 of the generator sideconverter 82B. The generator side control modules 81A and 81B includedin the wind power converter device 8 can use the method described inFIG. 5 to control the generator side converters 82A-82B.

Similarly, such an asymmetrical architecture can be used in the windpower converter device 1.

Reference is now made to FIG. 9. FIG. 9 is a circuit diagram of a windpower converter device 9 in an embodiment of the present disclosure.

The wind power converter device 9 includes grid side converters 90A-90B,a generator side converter 92A and a DC bus module. The grid sideconverters 90A-90B are connected in series. However, the generator sideconverter 92A in the wind power converter device 9 is a three-levelconverter. The grid side converters 90A-90B are two-level converters. Inthe present embodiment, the DC bus module includes two DC buses 900 and902 corresponding to the grid side converters 90A-90B and the generatorside converter 92A. The DC bus 900 is electrically coupled to the firstDC input IN1 of the grid side converter 90A and the first DC output OUT1of the generator side converter 92A. The DC bus 902 is electricallycoupled to the second DC input IN2 of the grid side converter 90B andthe second DC output OUT2 of the generator side converter 92A. The DCbus is not disposed between the second DC input IN2 of the grid sideconverter 90A and the first DC input IN1 of the grid side converter 90Band the intermediate output OUT0 of the generator side converter 92A.

In an embodiment, the wind power converter device is similar to the windpower converter device 9 illustrated in FIG. 9 but includes the DC busmodule that has the DC buses 900, 901 and 902. The DC bus 900 iselectrically coupled to the first DC input IN1 of the grid sideconverter 90A and the first DC output OUT1 of the generator sideconverter 92A. The DC bus 901 is electrically coupled to the second DCinput IN2 of the grid side converter 90A and the first DC input IN1 ofthe grid side converter 90B and the intermediate output OUT0 of thegenerator side converter 92A. The DC bus 902 is electrically coupled tothe second DC input IN2 of the grid side converter 90B and the second DCoutput OUT2 of the generator side converter 92A.

In an embodiment, the DC bus module further include bus capacitors C1-C4each electrically coupled between the first DC input IN1 and the secondDC input IN2 of the grid side converter 90A, between the first DC inputIN1 and the second DC input IN2 of the grid side converter 90B andbetween the first DC output OUT1, the intermediate output OUT0 and thesecond DC output OUT2 of the generator side converter 92A to support thevoltages of these terminals.

In an embodiment, the wind power converter device 9 further includeschopper circuits 93A and 93B. The chopper circuits 93A and 93B arerespectively disposed between the two ends of the bus capacitor C3 andthe two ends of the bus capacitor C4 to perform a voltage balancingprotection to the generator side converter 92A.

Similarly, such an asymmetrical architecture can be used in the windpower converter device 1.

Reference is now made to FIG. 10. FIG. 10 is a circuit diagram of a windpower converter device 10 in an embodiment of the present disclosure.The wind power converter device 10 includes grid side converters100A-100B, generator side converters 102A-102D and a DC bus module. Inan embodiment, the grid side converters 100A-100B are three-levelconverters and include identical components. The grid side converters100A-100B are electrically coupled to the grid 16 and are electricallycoupled in series. The second DC input IN2 of the grid side converter100A and the first DC input IN1 of the grid side converter 100B arecoupled in series.

In an embodiment, the generator side converters 102A-102D includeidentical components and are two-level converters. The generator sideconverters 102A-102D are electrically coupled to the generator device18. Any two of the neighboring generator side converters 102A-102D arecoupled in series through the first DC output OUT1 and the second DCoutput OUT2.

Take the generator side converters 102A and 102B as an example, thesecond DC output OUT2 of the generator side converter 102A is coupled inseries to the first DC output OUT1 of the generator side converter 102B.Similarly, the second DC output OUT2 of the generator side converter102B is coupled in series to the first DC output OUT1 of the generatorside converter 102C. Similarly, the second DC output OUT2 of thegenerator side converter 102C is coupled in series to the first DCoutput OUT1 of the generator side converter 102D.

The DC bus module includes DC buses 1000-1004. The DC bus 1000 iselectrically coupled to the first DC input IN1 of the grid sideconverter 100A and the first DC output OUT1 of the generator sideconverter 102A. The DC bus 1002 is electrically coupled to the second DCinput IN2 of the grid side converter 100B and the second DC output OUT2of the generator side converter 102D. The DC bus 1001 is electricallycoupled to the intermediate input IN0 of the grid side converter 100Aand the first DC output OUT1 of the generator side converter 102B. TheDC bus 1003 is electrically coupled to the second DC input IN2 of thegrid side converter 100A and the second DC output OUT2 of the generatorside converter 102B. The DC bus 1004 is electrically coupled to theintermediate input IN0 of the grid side converter 100B and the first DCoutput OUT1 of the generator side converter 102D.

Therefore, the generator side control modules 101A-101D included in thewind power converter device 10 can use the method described in FIG. 5 tocontrol the generator side converters 102A-102D.

In another embodiment, the DC bus module can only include two DC buses1000 and 1002 that correspond to the grid side converters 100A and 100Band the generator side converters 102A and 102D. The DC bus is notdisposed between the intermediate input IN0 of the grid side converter100A and the first DC output OUT1 of the generator side converter 102B,between the second DC input IN2 of the grid side converter 100A and thesecond DC output OUT2 of the generator side converter 102B and betweenthe intermediate input IN0 of the grid side converter 100B and the firstDC output OUT1 of the generator side converter 102D.

The generator side control modules 101A-101D included in such a windpower converter device 10 can use the methods described in FIG. 2 andFIG. 3 to control the generator side converters 102A-102D.

In an embodiment, the DC bus module further includes bus capacitorsC1-C8 each electrically coupled between the first DC input IN1 and theintermediate input IN0 and between the intermediate input IN0 and thesecond DC input IN2 of the grid side converter 100A-100B and between thefirst DC output OUT1 and the second DC output OUT2 of the generator sideconverters 102A-102D to support the voltages of these terminals.

In an embodiment, the wind power converter device 10 further includeschopper circuits 103A-103D. The chopper circuits 103A-103D arerespectively disposed between the two ends of the bus capacitors C3, C4,C7 and C8 to perform a voltage balancing protection to the generatorside converters 102A-102D.

FIG. 11 is a circuit diagram of a wind power converter device 11 in anembodiment of the present disclosure.

The wind power converter device 11 includes grid side converters110A-110D, generator side converters 112A-112B and a DC bus module. Inan embodiment, the grid side converters 110A-110D include identicalcomponents and are two-level converters. The grid side converters110A-110D are electrically coupled to the grid 16. Any two of theneighboring grid side converters 110A-110D are coupled in series throughthe first DC input IN1 and the second DC input IN2. Take the grid sideconverters 110A and 110B as an example, the second DC input IN2 of thegrid side converter 110A is coupled in series to the first DC input IN1of the grid side converter 110B.

Similarly, the second DC input IN2 of the grid side converter 110B iscoupled in series to the first DC input IN1 of the grid side converter110C. Similarly, the second DC input IN2 of the grid side converter 110Cis coupled in series to the first DC input IN1 of the grid sideconverter 110D.

In an embodiment, the generator side converters 112A-112B includeidentical components and are three-level converters. The generator sideconverters 112A-112B are electrically coupled to the generator device18. The second DC output OUT2 of the generator side converter 112A andthe first DC output OUT1 of the generator side converter 1126 arecoupled in series.

The DC bus module includes DC buses 1100-1104. The DC bus 1100 iselectrically coupled to the first DC input IN1 of the grid sideconverter 110A and the first DC output OUT1 of the generator sideconverter 112A. The DC bus 1102 is electrically coupled to the second DCinput IN2 of the grid side converter 110D and the second DC output OUT2of the generator side converter 112B. The DC bus 1101 is electricallycoupled to the intermediate output OUT0 of the generator side converter112A and the first DC input IN1 of the grid side converter 110B. The DCbus 1103 is electrically coupled to the second DC output OUT2 of thegenerator side converter 112A and the second DC input IN2 of the gridside converter 110B. The DC bus 1104 is electrically coupled to theintermediate output OUT0 of the generator side converter 112B and thefirst DC output OUT1 of the grid side converter 110D.

Therefore, the generator side control modules 111A-111B included in thewind power converter device 11 can use the method described in FIG. 5 tocontrol the generator side converters 112A-112B.

In another embodiment, the DC bus module can only include two DC buses1100 and 1102 that correspond to the grid side converters 110A and 110Dand the generator side converters 112A and 112B. The DC bus is notdisposed between the intermediate output OUT0 of the generator sideconverter 112A and the first DC input IN1 of the generator sideconverter 110B, between the second DC output OUT2 of the generator sideconverter 112A and the second DC input IN2 of the grid side converter110B and between the intermediate output OUT0 of the generator sideconverter 112B and the first DC input IN1 of the grid side converter110D.

In an embodiment, the wind power converter device 11 further includeschopper circuits 113A-113D. The chopper circuits 113A-113D arerespectively disposed between the two ends of the bus capacitors C3, C4,C7 and C8 to perform a voltage balancing protection to the generatorside converters 112A-112B.

The generator side control modules 111A-111B included in such a windpower converter device 11 can use the methods described in FIG. 2 andFIG. 3 to control the generator side converters 112A-112B.

Therefore, it is appreciated from the embodiments from FIG. 6 to FIG. 11that the design of the wind power converter device can be adjustedelastically according to the practical demands and is not limited to aspecific architecture.

FIG. 12 is a circuit diagram of a converter device 12 in an embodimentof the present disclosure.

The architecture of the converter device 12 is similar to that of thewind power converter device 7. However, the first generator sideconverters 120A-120B included in the converter device 12 are coupled inseries and are coupled to a motor device 124. The second generator sideconverters 122A-122B included in the converter device 12 are coupled inseries and are coupled to a generator device 126. The converter device12 in the present embodiment is used in the condition that the distancebetween the first generator side converters and the second generatorside converters is larger, such as the converter series-parallel systemused in the propeller of the ships. Moreover, the converter device 12includes the control modules 121A and 121B. The method described in FIG.5 can be used to control the second generator side converters 122A-122B.Converter device includes chopper circuits each is disposed between thetwo ends of the bus capacitors of the first generator side convertersand the second generator side converters.

Although the present disclosure has been described in considerabledetail with reference to certain embodiments thereof, other embodimentsare possible. Therefore, the spirit and scope of the appended claimsshould not be limited to the description of the embodiments containedherein.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentdisclosure without departing from the scope or spirit of the disclosure.In view of the foregoing, it is intended that the present disclosurecover modifications and variations of this disclosure provided they fallwithin the scope of the following claims.

What is claimed is:
 1. A wind power converter device comprising: a plurality of grid side converters each comprising a plurality of grid side outputs electrically coupled to a grid, a first direct current (DC) input and a second DC input, wherein the second DC input of one of any two of the neighboring grid side converters is coupled in series to the first DC input of another one of the two neighboring grid side converters; a plurality of generator side converters each comprising a plurality of generator side inputs electrically coupled to a generator device, a first DC output and a second DC output, wherein the second DC output of one of any two of the neighboring generator side converters is coupled in series to the first DC output of another one of the two neighboring generator side converters; and a DC bus module electrically coupled between the grid side converters and the generator side converters, wherein the grid side converters comprise a first grid side converter, a second grid side converter and at least one intermediate grid side converter, and the generator side converters comprises a first generator side converter, a second generator side converter and at least one intermediate generator side converter; the DC bus module comprises a first DC bus and a second DC bus, wherein the first DC bus is electrically coupled between the first DC input of the first grid side converter and the first DC output of the first generator side converter, and the second DC bus is electrically coupled between the second DC input of the second grid side converter and the second DC output of the second generator side converter.
 2. The wind power converter device of claim 1, wherein the DC bus module further comprises at least one intermediate DC bus electrically coupled between the first DC input of the intermediate grid side converter and the first DC output of the intermediate generator side converter.
 3. The wind power converter device of claim 1, wherein the DC bus module comprises a plurality of DC buses each electrically coupled to the first DC input of one of the corresponding grid side converters and the first DC output of one of the corresponding generator side converters and to the second DC input of one of the corresponding grid side converters and the second DC output of one of the corresponding generator side converters.
 4. The wind power converter device of claim 3, further comprising a plurality of generator side control modules each to receive a three phase input current amount of the generator side inputs of the generator side converters and a second axis general given current component to generate a three phase voltage control signal accordingly to control the corresponding generator side converters.
 5. The wind power converter device of claim 4, wherein each of the generator side control modules comprises: a current retrieving unit is configured to retrieve the three phase input current amount; a first converting unit is configured to convert the three phase input current amount to a first axis current component and a second axis current component; a first computing unit is configured to perform computation to generate a first axis difference according to the first axis current component and a first axis independent given current component; a second computing unit is configured to perform computation to generate a second axis difference according to the second axis current component and the second axis general given current component; a first current control unit to generate a first axis voltage control signal according to the first axis difference; a second current control unit to generate a second axis voltage control signal according to the second axis difference; and a second converting unit to convert the first axis voltage control signal and the second axis voltage control signal to the three phase voltage control signal.
 6. The wind power converter device of claim 1, wherein the DC bus module comprises a plurality of bus capacitors each electrically coupled between the first DC input and the second DC input of each of the grid side converters and the first DC output and the second DC output of each of the generator side converters.
 7. The wind power converter device of claim 1, wherein the grid side outputs of the grid side converters are coupled to the grid through a voltage transformer.
 8. The wind power converter device of claim 1, wherein the generator device comprises a multiple groups of windings each electrically coupled to the generator side inputs of the generator side converters.
 9. The wind power converter device of claim 1, wherein the generator device is a permanent magnet synchronous generator device, an excitation synchronous generator device or an induction generator.
 10. The wind power converter device of claim 1, wherein the number of the generator side converters is the same as the number of the grid side converters.
 11. The wind power converter device of claim 1, wherein each of the generator side converters is a two-level converter and each of the grid side converters is a two-level converter; or each of the generator side converters is a three-level converter and each of the grid side converters is a three-level converter.
 12. The wind power converter device of claim 6, further comprising a plurality of chopper circuits each electrically coupled to two ends of each of the bus capacitors.
 13. The wind power converter device of claim 1, further comprising a plurality of chopper circuit each electrically coupled to the first DC output and the second DC output of the generator side converters.
 14. A wind power converter device comprising: n grid side converters each comprising a plurality of grid side outputs electrically coupled to a grid, a first DC input, a middle point input and a second DC input; 2n generator side converters each comprising a plurality of generator side inputs electrically coupled to a generator device, a first DC output and a second DC output, wherein the second DC output of the 2n−1-th generator side converters is coupled in series to the first DC output of the 2n-th generator side converters; and a DC bus module electrically coupled between the grid side converters and the generator side converters; wherein n>=1.
 15. The wind power converter device of claim 14, when the number of the grid side converters is larger than 2, the second DC input of the n−1-th grid side converters is coupled in series to the first DC input of the n-th grid side converters.
 16. The wind power converter device of claim 14, wherein the DC bus module comprises 2n+1 DC buses, the 2n−1-th DC bus is electrically coupled between the first DC input of the n-th grid side converter and the first DC output of the 2n−1-th generator side converter, the 2n-th DC bus is electrically coupled to the middle point input of the n-th grid side converter, the second DC output of the 2n−1-th generator side converter and the first DC output of the 2n-th generator side converter, and the 2n+1-th DC bus is electrically coupled between the second DC input of the n-th grid side converter and the second DC output of the 2n-th generator side converter.
 17. The wind power converter device of claim 14, each of the generator side converters is a two-level converter and each of the grid side converters is a three-level converter.
 18. A wind power converter device comprising: 2n grid side converters each comprising a plurality of grid side outputs electrically coupled to a grid, a first DC input and a second DC input, wherein the second DC input of the 2n−1-th grid side converters is coupled in series to the first DC input of the 2n-th grid side converters; n generator side converters each comprising a plurality of generator side inputs electrically coupled to a generator device, a first DC output, a middle point output and a second DC output; and a DC bus module electrically coupled between the grid side converters and the generator side converters; wherein n>=1.
 19. The wind power converter device of claim 18, when the number of the generator side converters is larger than 2, the second DC output of the n−1-th generator side converters is coupled in series to the first DC output of the n-th generator side converters.
 20. The wind power converter device of claim 18, wherein the DC bus module comprises 2n+1 DC buses, the 2n−1-th DC bus is electrically coupled between the first DC input of the 2n−1-th grid side converter and the first DC output of the n-th generator side converter, the 2n-th DC bus is electrically coupled to the second DC input of the 2n−1-th grid side converter, the first DC input of the 2n-th grid side converter and the middle point output of the n-th generator side converter, and the 2n+1-th DC bus is electrically coupled between the second DC input of the 2n-th grid side converter and the second DC output of the n-th generator side converter.
 21. The wind power converter device of claim 18, each of the grid side converters is a two-level converter and each of the generator side converters is a three-level converter.
 22. A converter device comprising: a plurality of first generator side converters each comprising a plurality of motor side outputs electrically coupled to a motor device, a first DC input and a second DC input, wherein the second DC input of one of any two of the neighboring first generator side converters is coupled in series to the first DC input of another one of the two neighboring first generator side converters; a plurality of second generator side converters each comprising a plurality of generator side inputs electrically coupled to a generator device, a first DC output and a second DC output, wherein the second DC output of one of any two of the neighboring second generator side converters is coupled in series to the first DC output of another one of the two neighboring second generator side converters; and a DC bus module electrically coupled between the first generator side converters and the second generator side converters. 